1. Field of the Invention
The present invention relates to elastomeric materials comprising a material having a hardblock content of more than 50%, the elastomeric material having a density of more than 100 kg/m3 and comprising a plurality of urethane, urea and/or isocyanurate groups.
2. Background Information
Elastomeric materials having a density of at least 100 kg/m3 and comprising a plurality of urethane, urea and/or isocyanurate groups have been widely described. Most disclosures relate to the more traditional elastomers with regard to hardblock content, although hardblock content in these disclosures is not explicitly referred to. More traditional elastomers show a hardblock content between 25 and 40%.
Controlling the glass transition temperature and the hardness of these elastomers is done by varying the amount of polyols having a high molecular weight (and therefore the hardblock content of the elastomer). This requires careful balancing of reaction conditions and catalyst types and contents. Often different catalysts are required simultaneously in order to control the curing and the final properties of the material. Also the stream ratios between the polyisocyanate stream and the isocyanate-reactive material stream will change, often necessitating changes in mixing devices like changing injection nozzles. Alternatively or additionally plasticizers can be used when lowering the hardblock content would result in poor processing and mechanical properties like tear and tensile strength. Current practice is to use unreactive plasticizers like phthalates or other relatively low molecular weight, solvent-type materials. These plasticizers, however, show the tendency to exude over time which may give rise to a consequential degradation of material properties, fogging and a negative effect on the environment and health situation. Therefore plasticizers have been developed which show less tendency to migrate, like diurethane compounds having a high molecular weight, see e.g. U.S. Pat. No. 6,503,980, U.S. Pat. No. 6,384,130, U.S. Pat. No. 6,355,721 and U.S. Pat. No. 6,218,462.
U.S. Pat. No. 5,525,654 describes the use of diurethanes as plasticizers in sealing and/or adhesive compositions. The diurethanes may be the reaction products of diisocyanates and mono-functional alcohols, which may be selected from monoalkyl polyether alcohols. U.S. Pat. No. 4,824,888 also describes the use of diurethanes in sealings.
U.S. Pat. No. 6,355,721 relates to plasticizers comprising the reaction product of an isocyanate-terminated polyether prepolymer and a monofunctional alcohol having a molecular weight of about 32 to about 1000. The plasticizer has a high molecular weight and is liquid and non-migrating and is non-reactive; it is used in elastomers.
U.S. Pat. No. 6,218,462 relates amongst others to plasticizers made from polyisocyanates and mono alcohols having a molecular weight of more than 4000. They are used in elastomers.
EP 1104775 discloses the use of liquid, diurethane plasticizers made from a diisocyanate and a monoalcohol having a molecular weight of about 100 to about 1000. EP 1108735 and EP 1217021 also relate to polyurethane plasticizers.
PCT/EP2007/051335 discloses products which are obtained by reacting a diisocyanate, a monoalkoxy polyoxyalkylene monoamine and water. They are used as cell opener and rheology modifier.
Polyurethane Industry 2006, 21 (2): 1-3 discloses plasticizers made from diisocyanates, diols and monools and from monoisocyanates and monools.
Disclosures related to materials having a density of more than 100 kg/m3 and having a high hardblock content are less frequently made; examples are EP 912623, WO 02/10249, WO 04/111101, WO 07/042411 and WO 07/096216.
In a recent article by Harry Chen et al. presented at the CPI Technical Conference in Orlando, Fla., USA on 24-26 Sep. 2007 MDI semi-flexible foams having a very low density were made without polyols by reacting polyisocyanate and water in the presence of two non-reactive additives. The additives behave as plasticizers which soften the hard polymer matrix and provide flexibility to the foams. Chen does not disclose the chemical nature of the additives.
GB 2028356 discloses the use of monohydroxy-terminated polybutadiene as plasticizer in polyurethanes and in particular in polyurethane elastomers.
U.S. Pat. No. 4,265,798 discloses isocyanurate cross linked polyurethanes having a hardblock content of 100%.